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Thomas S Varley - One of the best experts on this subject based on the ideXlab platform.
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in situ spectroelectrochemistry and colour measurement of a complementary electrochromic device based on surface confined prussian blue and aqueous solution phase methyl viologen
Solar Energy Materials and Solar Cells, 2012Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:Abstract The fabrication, in situ spectroelectrochemistry and colour measurement of hybrid electrochromic devices (ECDs) based on a surface-confined metal hexacyanometallate – Prussian blue (PB, containing the iron(III) hexacyanoferrate(II) chromophore) – and aqueous solution-phase methyl viologen ( N , N ′-dimethyl-4,4′-bipyridylium) are described. In the ECDs, the initial (‘off’) bleached State is set with PB in its reduced form and the methyl viologen as the di-cation. Switching to the Coloured State (‘on’), forms the mixed-valence iron(III) hexacyanoferrate(II) chromophore upon oxidation of iron(II) hexacyanoferrate(II), with simultaneous reduction of the methyl viologen di-cation to form a mixture of the radical cation monomer/dimer. Using the Commission Internationale de l'Eclairage (CIE) system of colorimetry, the colour stimulus of such ECDs and the changes that take place on reversibly switching between the colourless and Coloured States have been calculated from in situ visible region spectra recorded under electrochemical control. The concentration of the solution-phase methyl viologen and its diffusion to the cathode controlled both the proportion of surface-confined (reduced) PB that is switched to the blue form and the overall ECD changes. For the ECDs' ‘on’ States, the CIELAB 1976 colour space coordinates for a D55 illuminant were L ⁎ =60, a ⁎ =3 and b ⁎ =−46, and L ⁎ =49, a ⁎ =9 and b ⁎ =−59, respectively for 5 and 10 mM methyl viologen solution concentrations. The low a ⁎ and high (negative) b ⁎ chromaticity coordinates quantified the overall ECD colour stimulus of the ‘on’ State as being deep blue, with a broad absorption across the visible spectral region. CIELAB 1976 colour space coordinates showed that the ECDs were fully transparent and nearly colourless in the ‘off’ States, with L ⁎ =100, a ⁎ =1 and b ⁎ =1. The changes in the transparency were 83.0% (5 mM methyl viologen) and 93.1% (10 mM methyl viologen) between the ‘off’ (bleached) and ‘on’ (Coloured) States of the ECDs.
Roger J Mortimer - One of the best experts on this subject based on the ideXlab platform.
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in situ spectroelectrochemistry and colour measurement of a complementary electrochromic device based on surface confined prussian blue and aqueous solution phase methyl viologen
Solar Energy Materials and Solar Cells, 2012Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:Abstract The fabrication, in situ spectroelectrochemistry and colour measurement of hybrid electrochromic devices (ECDs) based on a surface-confined metal hexacyanometallate – Prussian blue (PB, containing the iron(III) hexacyanoferrate(II) chromophore) – and aqueous solution-phase methyl viologen ( N , N ′-dimethyl-4,4′-bipyridylium) are described. In the ECDs, the initial (‘off’) bleached State is set with PB in its reduced form and the methyl viologen as the di-cation. Switching to the Coloured State (‘on’), forms the mixed-valence iron(III) hexacyanoferrate(II) chromophore upon oxidation of iron(II) hexacyanoferrate(II), with simultaneous reduction of the methyl viologen di-cation to form a mixture of the radical cation monomer/dimer. Using the Commission Internationale de l'Eclairage (CIE) system of colorimetry, the colour stimulus of such ECDs and the changes that take place on reversibly switching between the colourless and Coloured States have been calculated from in situ visible region spectra recorded under electrochemical control. The concentration of the solution-phase methyl viologen and its diffusion to the cathode controlled both the proportion of surface-confined (reduced) PB that is switched to the blue form and the overall ECD changes. For the ECDs' ‘on’ States, the CIELAB 1976 colour space coordinates for a D55 illuminant were L ⁎ =60, a ⁎ =3 and b ⁎ =−46, and L ⁎ =49, a ⁎ =9 and b ⁎ =−59, respectively for 5 and 10 mM methyl viologen solution concentrations. The low a ⁎ and high (negative) b ⁎ chromaticity coordinates quantified the overall ECD colour stimulus of the ‘on’ State as being deep blue, with a broad absorption across the visible spectral region. CIELAB 1976 colour space coordinates showed that the ECDs were fully transparent and nearly colourless in the ‘off’ States, with L ⁎ =100, a ⁎ =1 and b ⁎ =1. The changes in the transparency were 83.0% (5 mM methyl viologen) and 93.1% (10 mM methyl viologen) between the ‘off’ (bleached) and ‘on’ (Coloured) States of the ECDs.
F Simone - One of the best experts on this subject based on the ideXlab platform.
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an electrochromic device working in absence of ion storage counterelectrode
Solar Energy Materials and Solar Cells, 1995Co-Authors: Agostino Pennisi, F SimoneAbstract:Abstract The fabrication and the characterization of a full solid State electrochromic device are discussed. The peculiarity of the realized device is the absence of a specific ion storage counterelectrode, in fact a film of an electrochromic material (EC) is interfaced and coupled with a particular ion conducting solid polymer and a second conducting layer. This kind of structure greatly simplifies the procedure of fabrication. The EC is Tungsten trioxide doped with Molybdenum oxide, electrochemically deposited on ITO coated glass. The electrolyte is a polymer film of Nafion-H™ (Trade Mark of E.I. Du Pont de Nemours). The presence of Nafion-H (hydrogenated form of Nafion), which has a very high proton concentration, totally avoids the necessity of presence of another component. Moreover, in the assembling procedure of the device, it is not necessary to charge preventively the electrochromic and/or the ion storage counterelectrode. The second electrode is constituted by another ITO coated glass. The realized device switches between the dark blue and transparent State with a low value of applied potential ranging from −4 upto 2 V. Different waveform potentials have been tested in the past in order to find the optimum bias conditions to operate between stable phases. Previous experimental results indicate the trapezoidal waveform potential as the most convenient one. The visible optical transmittance in the bleached and Coloured State has been measured and has given the following values: Tv(blached) = 57.7% and Tv(Coloured) = 8.4%. Taking also into account the magnitude of the exchanged charge (≅ 12.8 mC/cm2), these values of transmission give a very good coloration efficiency. Dynamical measurements evidence an acceptable switching rate, in fact the typical switching time for the bleaching process is about 20 s, while a somewhat longer time is necessary for coloration. The device exhibits quite good long memory properties and chemical stability.
Khoo, Steffi Shu Fern - One of the best experts on this subject based on the ideXlab platform.
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Smart windows for modulation of infrared heat
'Nanyang Technological University', 2020Co-Authors: Khoo, Steffi Shu FernAbstract:Smart windows technologies have been an area of great research interest to minimize energy consumption from commercial and residential buildings. Smart windows are known to have high energy efficiency and adaptability in climate change and are often classified as electrochromic, photochromic or thermochromic windows. Prior research on electrochromic windows have found that Tungsten Trioxide (WO3) is the best electrochromic material and that Electrochromic Photonic Crystals (EPC) technology involved periodic inverse opal (IO) structures that can enhance the modulation of infrared radiation. Previous studies on TiO2-WO3 and SnO2-WO3 hybrid systems have achieved several improvements for electrochromic performance. However, those compositions remain limitations of transparency, electrochromic stability. A novel MoxSnO2/ α-WO3 EPC framework is thus fabricated to block at least 80% NIR radiation in the Coloured State, enables up to 90% of visible light transmittance in bleached State and retain the electrochromic stability for at least 900 cycles. In this project, the novel MoxSnO2 EPC is fabricated and tested to optimize the concentration of Molybdenum (Mo). The results have shown that 20 mol.% Molybdenum is the optimal concentration.Bachelor of Engineering (Materials Engineering
Agostino Pennisi - One of the best experts on this subject based on the ideXlab platform.
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an electrochromic device working in absence of ion storage counterelectrode
Solar Energy Materials and Solar Cells, 1995Co-Authors: Agostino Pennisi, F SimoneAbstract:Abstract The fabrication and the characterization of a full solid State electrochromic device are discussed. The peculiarity of the realized device is the absence of a specific ion storage counterelectrode, in fact a film of an electrochromic material (EC) is interfaced and coupled with a particular ion conducting solid polymer and a second conducting layer. This kind of structure greatly simplifies the procedure of fabrication. The EC is Tungsten trioxide doped with Molybdenum oxide, electrochemically deposited on ITO coated glass. The electrolyte is a polymer film of Nafion-H™ (Trade Mark of E.I. Du Pont de Nemours). The presence of Nafion-H (hydrogenated form of Nafion), which has a very high proton concentration, totally avoids the necessity of presence of another component. Moreover, in the assembling procedure of the device, it is not necessary to charge preventively the electrochromic and/or the ion storage counterelectrode. The second electrode is constituted by another ITO coated glass. The realized device switches between the dark blue and transparent State with a low value of applied potential ranging from −4 upto 2 V. Different waveform potentials have been tested in the past in order to find the optimum bias conditions to operate between stable phases. Previous experimental results indicate the trapezoidal waveform potential as the most convenient one. The visible optical transmittance in the bleached and Coloured State has been measured and has given the following values: Tv(blached) = 57.7% and Tv(Coloured) = 8.4%. Taking also into account the magnitude of the exchanged charge (≅ 12.8 mC/cm2), these values of transmission give a very good coloration efficiency. Dynamical measurements evidence an acceptable switching rate, in fact the typical switching time for the bleaching process is about 20 s, while a somewhat longer time is necessary for coloration. The device exhibits quite good long memory properties and chemical stability.